Undercover
by jackwabbit
Summary: Gen. Humor. Friendship/Family. Sherlock, John, and Mycroft. Series: Any, but likely early on. Spoilers: None. Summary: John always considered Sherlock and Mycroft barely human, and now he knows why. Note: This one is a bit silly, and it's all for Lowell, who understood my offhand comment. Also, a knowledge of Star Trek physiology is helpful here.


**Undercover**

Rated: G

Category: Gen. Humor. Friendship/Family. Sherlock, John, and Mycroft.

Series: Any, but likely fairly early on.

Spoilers: None.

Summary: John always considered Sherlock and Mycroft barely human, and now he knows why.

Note: This one is a bit silly, and it's all for Lowell, who understood my offhand comment. Also, a knowledge of Star Trek physiology is helpful here.

xxx

Sherlock Holmes crossed his arms over his chest and stared John Watson down.

"It doesn't make sense," he deadpanned.

John sighed and absently turned a page of his newspaper. "It's just an expression, Sherlock."

"But it doesn't make sense."

"Neither do a lot of expressions!" said John, giving up on the paper.

"True," conceded Sherlock, "but most of them have their origin in something that once did. This doesn't."

John buried his face in his hands. "We didn't always know what we know now, Sherlock!"

"That hardly matters," answered Sherlock, flipping his hand in dismissal.

That was enough to bring John's head back up in irritation.

"How do you figure that?" he argued.

"Because," said Sherlock, "by being specific in the expression, we implied that we knew the taste of specific metals. If we, as a species, knew that, then we knew enough to know that blood does not taste like copper, but like iron. After all, who hasn't bitten their tongue? Even before we knew blood was iron-based, we knew its taste. And if we knew the taste of copper specifically enough to use it as a descriptor, one can assume we also knew the slightly different taste of iron and therefore we should have used the correct terminology, or at least evolved it shortly thereafter. But no. We didn't and, worse, still don't. Oh, I fear for the species."

John blinked at Sherlock in utter amazement. "Don't you think you're taking this a bit too far?"

"No! The phrase makes no sense, John! Blood does not taste like copper! It tastes like iron! It's iron-based! You're a doctor! You should know these things! Iron, not copper!"

Suddenly, a disembodied voice broke into the conversation.

"Unless you're a Vulcan," it said.

Sherlock answered without thinking. He turned his head toward the hallway and its wide open door as he spoke and John welcomed the reprieve from Sherlock's glare. "Well, of course. That's a given. Let's assume, then, for the purposes of this argument, that all subjects are human."

"Granted," said the voice, just as Mycroft came into view. "Though you should have specified that in your original statement."

"Details, Mycroft," answered Sherlock, clearly moving on. He turned back to John, but Mycroft's voice stopped him mid-motion.

"So says the man who lives by them," Mycroft said. He arched an eyebrow at his brother in obvious challenge.

Sherlock whirled back around and mirrored Mycroft's expression with a raised brow of his own, and to anyone familiar with the Holmes brothers, it was evident a fight was coming.

But before the silent argument could escalate to more, a stifled chuckle broke the quiet and both Holmes men turned to regard John Watson.

"Something funny, John?" asked Sherlock.

John shook his head and bit his lip for a moment before he answered. "Nope. Sorry. Funny thought is all. Something in the paper." He held up the newspaper in his lap as a defense.

"Oh," said Sherlock. "Now, where were we, Mycroft?"

"I believe we were discussing your inattention to detail in this particular case, Sherlock. But forget about that. I have more important things to discuss with you."

Sherlock arched a brow again in interest and the same stifled chuckle came from the chair containing John. Both Sherlock and Mycroft sent a glare John's way but said nothing else, and soon Mycroft laid out the details of the latest case he wanted Sherlock's help with. John grew interested and joined them at the table within minutes, but despite all the looks the Holmes brothers kept casting his way, he still occasionally let loose a giggle. He explained every one of them away, and though he was certain neither genius entirely believed his reasons, he was glad they didn't press the matter further.

For he had learned two things that day that would amuse him for months, if not years, and he strongly preferred to keep them to himself if at all possible.

One, both Sherlock and Mycroft Holmes were so well-versed in Star Trek that it was second nature to them; and two, every time one of them (or better yet, both of them simultaneously) lifted a single eyebrow to their hairline, he'd never be able to completely stifle the laugh that bubbled inside of him.

Because while John Watson had always considered Sherlock and Mycroft Holmes barely human, it wasn't until then that he knew exactly why: from that day forward no one would convince him they weren't undercover Vulcans.


End file.
